For these tech pioneers, a decent ROI is only part of the mission.

MINYANVILLE ORIGINAL In the past, Minyanville has taken a look at former corporate executives who ditched their corner offices; powerful men and women who fished and caught the big one but decided -- via epiphany, spiritual awakening, or stomach ulcer -- to cut bait for far more placid waters.

While those particular dropouts left big business for more virtuous pursuits, like joining the priesthood or volunteering in refugee camps, there are still others, especially those reared in Silicon Valley, who defect for the cause of innovation. Find out who among the tech ranks has given it all up in order change the world -- or at least make it a better place -- one start-up at a time.

Chamath Palihapitiya, Founder of The Social+Capital Partnership
From his cushy beanbag chair at Facebook (NASDAQ:FB) where he was one of the social network’s founding executives, Chamath Palihapitiya made a beeline for the giving side of venture capital. Ruled by his trademark “risk-on” mentality and a desire to shake up what’s not working, Palihapitiya partnered with elite funders in philanthropy, private equity, technology, and corporate sectors to force positive, systemic change into the stodgier pillars of society. It’s not so much to knock them down, but, perhaps, reposition and reinforce them so they’ll stand higher and mightier in the future.

With nearly $300 million in the main fund and “unlimited” side project capital, Palihapitiya et al have set out to reinvent health care, education, and Wall Street using high-tech devices and applications. One of their latest ventures is medical diagnostics. A $3 million investment in a start-up called Integrated Plasmonics could help revolutionize how we test for diseases by measuring cholesterol and glucose levels, blood count, kidney functions, etc. -- all in a single, inexpensive instrument.

“The idea would be: You have this little strip, you could lick it, you could pee on it, or you could put a microdrop of blood on it, stick it into this little machine, and it’ll do a full characterization,” Palihapitiya told Bloomberg. “You can basically know every day, every week, every month, everything that’s happening in your body.”

Integrated Plasmonics is just one of many start-ups Palihapitiya and his elite group of fellow investors have decided to fund. For a look at their other investments, see "Do Gooder Investments" here.

Nathan Blecharczyk, CTO & Co-Founder of Airbnb
In August of 2008, a former program manager at Microsoft (NASDAQ:MSFT) and engineer at OPNET Technologies (NASDAQ:OPNT) took a huge gamble to start a brand new enterprise designed to upend the hotel industry. Within three short years, that company reached a major valuation milestone at $1 billion. Today it’s worth 150% more and even has PayPal’s (NASDAQ:EBAY) Peter Thiel looking for a piece of the “sky high” pie.

Airbnb, a marketplace that connects travelers with unused private rooms, apartments, and homes, has booked over 10 million nights in 192 countries around the globe. In a sluggish economy, the site is not only saving travelers money, but also giving local marketplaces a huge revenue boost. A study conducted by HR&A Advisors found that Airbnb travelers dropped $56 million over the course of a year in San Francisco alone while making hosts an average of $9,300 in annual income for renting their homes ($6,900 for those offering shares). Moreover, 72% of Airbnb properties in San Francisco are in “off the beaten track” neighborhoods that don’t normally enjoy tourist dollars.

Recently, we saw how the service leveraged its network for good in the midst of the homeless crisis created by Hurricane Sandy. A Discounted Sandy Listings page was created with all associated fees waived by the company.

Shai Agassi, Founder of Better Place
Better Place has seen better days. Founder Shai Agassi, former president of the products and technology group at SAP AG (NYSE:SAP), formed the the Palo-Alto start-up in 2007 with ambitions to break the world’s addiction to oil. In five years, he managed to raise nearly $1 billion to build networks of electric car fueling stations and saw his switchable-battery model become a reality in Israel and Denmark, with operations underway in Australia, China, and Japan.

But, recently -- amid high costs and low sales that resulted in losses of $490 million and layoffs in the hundreds -- Agassi was ousted as the CEO of Better Place.

Still, the company is moving forward -- and specifically moving to its home state. A partnership with the Metropolitan Transportation Commission will bring four battery switch stations to the San Francisco-San Jose corridor over the next three years to support zero-emission, electric taxis. The hope is that these early adopter vehicles will cause a ripple effect in the area. As Better Place states on its site, “Taxis are a high-mileage, high-visibility segment that can serve as the on-ramp for technology transfer to the mass-market.

Dr. Greg Raleigh, Founder & CEO of ItsOn
A potentially powerful mobile startup with data providers in its crosshairs, ItsOn hopes to have seen the telecom industry data-gouge its last account. Once its proprietary technology becomes available, cloud service and handset software will allow customers to cherry-pick their service based on individual need while, at the same time, opening the wireless market to a competitive new slew of devices and business models.

"Mobile service consumers are finally empowered to choose exactly which mobile services they need and how much they want to spend -- eliminating over-charging and bill shock," ItsOn founder and CEO Dr. Greg Raleigh said in a statement. "Consumers can select, monitor, control, and share all of their mobile services as they wish, instantly from their phone, tablet or PC without the inconvenience of talking to a sales associate, calling a support center, or logging into a website.”

A 30-year innovator and entrepreneur in networking solutions, Raleigh has four successful wireless companies under his belt as well as VP positions at Qualcomm (NASDAQ:QCOM) and Cisco (NASDAQ:CSCO).

In October, ItsOn got $15.5 million closer to achieving its goal when Series B financing came through from venture capital firm Andreessen Horowitz and investment company SV Angel.

Salman Khan, Founder & Executive Director of Khan Academy
As Bill Gates put it, Salman Khan “was a hedge fund guy making lots of money... I'd say we've moved about 160 IQ points from the hedge fund category to the teaching-many-people-in-a-leveraged-way category. It was a good day his wife let him quit his job.”

A career that started with three degrees from MIT, an MBA from Harvard, and a management position in the financial sector eventually led to the founding of Khan Academy -- an online learning institute that’s educating the world, 100% tuition-free. A library of over 3,600 10-minute lectures in math, science, the humanities, history, and finance (all taught by the eloquent and charismatic Khan) has been accessed via its YouTube channel over 214 million times by individual students, entire classrooms, and yes, even the former head of Microsoft (NASDAQ:MSFT). Google (NASDAQ:GOOG) and the Bill and Melinda Gates Foundation have made significant financial donations to the site.

And did we mention that the lessons, delivered by an Ivy League graduate four-times over, don’t cost a dime?

Beat that, University of Phoenix.

Dan Parham, Co-Founder & Designer of Neighborland
When most users are posting status updates asking for haircut tips or complaining about sinus infections, it’s sometimes hard to see how the world is better off for having Facebook. But when you localize social networks into action-oriented, community-specific sites aimed at improving the lives of its members, the societal benefit is a no-brainer.

That was the thinking that plucked Dan Parham from the secure embrace of Yahoo (NASDAQ:YHOO), as its director of user experience, to the very fickle arms of the start-up space.

“Neighborland started with a simple question: What if we could we see what the people in our neighborhood really wanted?” he says on the website. "[I, Candy Chang, and Tee Parham] built Neighborland to answer this question. Now we’re focused on turning ideas into action.”

So far, Neighborland sites have made real, substantive change in cities like Houston where a dangerous traffic light was reprogrammed and New Orleans where the transit authority launched its first mobile transit app. Currently, San Francisco’s Neighborland is mobilizing to get the city to build solar charging stations, Kansas City’s wants trees planted in urban areas, and Floridians are asking for expanded Metrorail service.

Evan Williams, Co-Founder of Obvious Corporation
Inventing the word “blogger” along with one of the first web applications for publishing weblogs, is a laurel on which one could comfortably rest for a lifetime. But if you’re entrepreneur Evan Williams, that’s just the start of your earth-shattering accomplishments.

In 2003, Williams officially made it when Google acquired his San Francisco-based Pyra Labs for its blog-writing service, Blogger. “I couldn't be more excited about this,” he told SiliconValley.com. A year later he was already moving on -- not to Apple or Microsoft or Samsung -- but to do his own thing, born out of a unique vision for democratizing news and information. This time, he’d continue to carry out his goal via a podcasting company called Odeo. Next up, Obvious Corporation and a little communications platform called Twitter.

Today, under the Obvious umbrella, Williams and partner Biz Stone continue to “build systems that help people work together to make the world a better place.” The company also invests in startups with which it considers itself “philosophically aligned.” Among that elite group? Neighborland.

No positions in stocks mentioned.

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